Managing Oak Leaf Blister Disease

Oak leaf blister, a disease caused by the Taphrina caerulescens fungus, has been quite active this spring and the cool wet weather lasting well in to late spring has provided the optimum environment for the development of this disease. As most oak species in our region are susceptible to the oak leaf blister disease, it is mainly water oaks and southern red oaks that have been most severely affected.

This fungal disease infects the leaves by causing water soaked depressions to develop on the underside of the leaf that in turn promotes blister-like bulges to develop on the upper surface of the leaf. Later the blisters turn brown and the infected leaves fall off the tree. By the time you see or realize the symptoms there is nothing to be done except to rake as the infection is already present and spreading at this point.

Fortunately, oak leaf blister is not life threatening to the tree. The leaves that drop and blanket the landscape are messy but there are no long term detrimental effects to the trees that homeowners should be worried about. In other words oak leaf blister disease will create some stress on infected trees because of less leaves to conduct photosynthesis, but the affected trees will not die as a result. Trees with oak leaf blister often re-bud and grow new leaves very quickly in response to shedding of the infected leaves.

Keep in mind that oak leaf blister is actually a very common disease and will be more prevalent in some years and may not be seen in other years. For this reason, preventative spraying is generally not conducted and is certainly not practical for homeowners with large mature trees. There are ways in helping to reduce the occurrence of this disease that would include raking and disposing of fallen leaves and twigs, keeping trees nutritionally fed through proper fertilization and periodic pruning that maintains good airflow and sunlight penetration throughout the canopy. Good sanitation and proper cultural practices will serve as an integral part in managing this disease.

Rene’ Schmit is the LSU AgCenter County Agent for St. Charles and St. John Parishes and can be reached at 985-785-4473 or 985-497-3261.